GENERAL INFORMATION
A neurofibroma is a benign tumor of the peripheral nerves, also known as solitary neurofibroma. Neurofibromas can arise as solitary entities or as part of a syndrome, namely neurofibromatosis. Neurofibromatosis is a genetic disease where patients develop multiple peripheral nerve tumors (neurofibromas and schwannomas) as well as cutaneous manifestations. A neurofibroma is not related to fibromatosis which is an entirely different entity
CLINICAL DATA
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Benign peripheral nerve tumor
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May be a single lesion
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Develops during childhood
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Close to 5% can transform to MPNST usually only in setting of neurofibromatosis
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As an isolated tumor (not in setting of neurofibromatosis)
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Non-familial incidence
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Little malignant change
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Little recurrence
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More common
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These are superficial tumors of the dermis:
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Orbit
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Face
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Neck
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Back
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Inguinal area
DIFFERENTIAL DIAGNOSIS
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MPNST
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Schwannoma (neurileoma)
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Neurofibroma
CLINICAL PRESENTATION
Sign/Symptoms
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Slow-growing and usually small
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Painless nodule
Prevalence
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No predilection for sex or race
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Somewhat rare
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Usually between 20 and 30 years
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Other age could be affected as well
Site
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Distributed throughout body surface
RADIOGRAPHIC PRESENTATION
X ray
o May reveal soft tissue mass
o Displacement of neurovascular bundle may also be apparent
CT
o Fusiform shape
o Nerve can often be seen entering/exiting the mass
o Perilesional rim
MRI
o Tubular structure
o Discrete margins, but sometime noticeable low signal intensity rim
o Attenuation lower than the muscle
o Signal intensity similar to or higher than skeletal muscle in T1W
o High signal intensity in T2W
Fig. 1 Axial MRI of a large neurofibroma of lower extremity
PATHOLOGY
Gross
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Gray-white
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Deep tumors are often large
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Can resemble a “bag of worms” refrred to as a plexiform neurofibroma
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Lack secondary degenerative changes
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Found in schwannomas
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If found in major nerves
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Expand structures in fusiform manner
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Normal nerve can be seen entering/exiting
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If contained by epineurium--->Possesses true capsule
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Usually appear circumscribed but are nonecapsulated
Fig. 2 Gross photograph of gray-white ovoid specimen after resection
Microscopic
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Interlacing bundles of cells
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Elongated cells
Wavy, dark-staining nuclei
Intimately associated with collagen
Small to moderate amounts of mucoid separate cells and collagen
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Stroma of tumor dotted with occasional
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Mast cells
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Lymphocytes
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Sometimes xanthoma cells
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May be more cellular
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With schwann cells, but no biphasic pattern
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Uniform collagen matrix devoid of mucosubstances
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Cells arranged in fascicles, whorls, or storiform pattern
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May contain Antoni A areas
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Not encapsulated so can be distinguished from schwannoma
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Involves the nerve fascicles; does not arise at periphery like a schwannoma and displace the fascicles
Fig. 3 Low power magnification shows wavy elongated schwann cells resembling nerve tissue
IMMUNOHISTOCHEMISTRY
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Positive for:
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S100 (scattered)
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EMA
PROGNOSIS
BIOLOGICAL BEHAVIOR
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Usually arises in small nerves in the skin
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Readily extend into soft tissue
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Rarely see malignant change with isolated neurofibromas
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Low recurrence rate after surgery (even complete resection)
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No metastasis
TREATMENT
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Simple excision, usually adequate
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Radiotherapy:
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May be considered, but not usually necessary
